Chapters 0-2 Chem 1110 - 02
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This 11 page Class Notes was uploaded by Corey Stewart on Wednesday September 14, 2016. The Class Notes belongs to Chem 1110 - 02 at East Tennessee State University taught by Dr. Greg Love in Fall 2016. Since its upload, it has received 98 views. For similar materials see General Chemistry in Chemistry at East Tennessee State University.
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Date Created: 09/14/16
CH. 0 Atomic Theory Everything is made of atoms. Brought about by careful observation in lab - Greek Philosophers just thought. Atoms smallest particle that describe element Proportions are definite Mass is conserved All things are made of tiny, indestructible particles called atoms Atoms of same element are exact same Different atoms of different elements are different Atoms come together in specific ratios Proton # = atomic # Protons and neutrons similar in mass - Mass number of 1 Electron mass insignificant - 1/1800 or 1/2000 of proton/neutron Most mass is proton and neutrons Protons dictate element (atomic #) Protons(Z) + Neutrons(N) = Mass # (A) Z = # of protons Charge: Protons (+), Electrons (-), Neutrons (±) Number of protons and electrons (e ) are equal which makes the atom neutral Atomic symbols notation – Superscript before means mass number ( H), subscript before is atomic number ( 1) 1 atomic mass unit (amu) is1 the mass of a Carbon – 12 (C – 12) atom 12 To find atomic mass take the known isotopes and multiply each by the percent abundance of the of the isotope. You will get a decimal and ten you add the decimated numbers together. CH. 1 Scientific Method 1. Make observations/collect data 2. Make a hypothesis 3. Test 4. Collect data 5. Repeat Law – Usually an equation, based on lots of tests, only what happens not why Hypothesis – Mental pic that explains laws, tentative explanation, prediction, leads to tests Hypothesis can challenge your view of the world and teach you something Will prove or disprove what you think Theory – tested explanation, devise more tests, modifiable, never actually absolutely correct Matter anything that has mass and takes up space Mass – measure of matter in a given object, measure of momentum/resistance to change in motion Weight – Measure of the pull of gravity on an object Matter and Elements Chemical Reactions – Change in chem composition Decomposition – Chem reaction, breaking down of substance Elements can’t be broken down to simpler materials by chemical means Elements are (usually) found as only one atom in nature Simplest form of matter Chemical Symbol one or two letters First capital second not (Helium is He) Used to represent elements in chemical reactions (2H +2O = 2H O) 2 Most based on English Some based on Latin (Fe for iron) or German (W for Tungsten) Compound two or more different atoms Fixed ratios Can be broken down Pure substance – Elements and compounds, composition always the same no matter where it’s found Mixture – Variable comps, two or more substances Homogeneous or Heterogeneous Homogeneous: Same properties throughout - Solution (ex. Coke (w/o ice), Metal alloys [nickel coin], the air around us) Solvent is chemical found in largest proportions, solute lesser proportions Heterogeneous: Two or more regions of different props (ex. A Mixture) Physical or Chemical Change Physical Change: No new substance form: change of state or proportions Matter – Solid (fixed shape, particles close together, restricted motion), liquid (fixed volume but take shape of container, particles close but not as close as solid, able to flow), gas (no fixed shape or volume, completely separate) Physical properties – props that can be observed w/o changing chem makeup (color, electrical conductivity) Chemical properties – describes reactivity, new substance has new props than independent elements Intensive Properties – Independent of sample size, used as identifier (color, density, melting and boiling point) Extensive Properties – Dependent on sample size (volume and mass) Observations Quantitative- numbers Qualitative- Physical properties Measurements Measurement involve comparison- Always measure relative to reference, Measurement= # + unit, measurement useless w/o unit Measurements are inexact- always have uncertainty, uses estimation, observer and instrument have physical limitations SI Units- International units used for measurements in a lab, recognized regardless of nationality, gives all scientists ability to communicate results 2 All physical quantities have derived units based on SI units (e.g. m ) Prefixes used on SI units when # is really big (1,000 grams is 1 kilogram) or really small (.01 meter is 1 centimeter) All measurements inexact Sources of error (e.g. human error) Ways to minimize error – take lots of measurements, data clusters around ventral value, calculate avg or mean, report average Significant Digits All digits up to and including the first estimated digit are significant Zeros to the right of the decimal. However, zeros to the right of the decimal and to the left of a non-zero digit are not significant Accuracy How close am I to the true value? Precision How close are my measurements to each other? Significant Figures in Calculations Multiplication and Division - Significant dig. in answer = number of significant digits in least precise measurements Addition and Subtraction - Answer has same decimal places as measurement with fewest decimal places Exact Numbers Numbers from defs. Numbers from direct count No uncertainty Infinite sig. fig. Don’t affect number of sig. figs. in multiply or divide Dimensional Analysis Use units to analyze prob. Not all cal. use equations - Conversion Factor --- Fraction formed by equivalence between units (2.54 cm/1 in.) --- Used to switch between one system of measurement to another Density Ratio of mass to volume Intensive prop (Size independent) Ratio of two dependent props leads to independent prop Sample size cancels g/mL or g/cm 3 Most substances expand slightly when heated - Same mass - Larger volume - Less dense Density down as temp up - Liquid and solid change is small - Can ignore change except in precise calculations Density useful to transfer b/t volume and mass Specific Gravity Ratio of density of substance to density of H O 2 Unitless Way to avoid tabulation of densities in different units Importance of Reliable Measurements To trust conclusions drawn from measurements - Must know they are reliable - Must know they are accurate --- Measured results must be close to true measurement - Must have sufficient precision --- Confident that two measurements are same for two samples --- Difference must be close to uncertainty CH. 2 Periodic Table Summarizes periodic properties of elements Early Versions Arranged by atomic mass Mendeleev and Meyer had the first periodic table Based on repeating properties Modern Periodic Table Arranged by atomic number Rows are periods Columns groups or families - ID’d by numbers - 1-18 standard international - 1-8A are the taller columns and 1-8B are the shorter columns Molecules and Chemical Formulas Atoms form compounds Formulas useful to visualize atoms, compounds and molecules Atoms are spheres when structuralized In a structure different atoms = different colors Molecules Atoms combine to form more complex substances Discrete particles Each composed of two or more atoms Ex. O ,2CO ,2NH ,3C H12 22 11 Chemical Formulas Specify composition Use chem symbols Subscripts after symbol show how many - Free Elements Element not combine with another in compound Just use chem symbols - Diatomic Molecules Molecules composed of two of same atom Many in Nature (O )2 3 Ways to Show Molecules Structural Ball-and-Stick Space filling Hydrates Crystals that contain water Water not tightly held Dehydration - Water removed by heating - Anhydrous remains Counting Atoms 1. Subscript after chem sym = # of atoms 2. Subscript after () = # of atoms (Multiply inside parentheses if necessary) 3. Raised dot shows Hydrate (MgSO • 7H O) 4 2 Dalton’s Theory All molecules of compound are alike and contain atoms in DEFINITE PROPORTIONS (H O; 2 ALWAYS 2H:1O; Mass of O is ALWAYS 8 times greater than H) Explains Law of Conservation of Mass - One side = the other Explains Law of Definite Proportions - Given compound always has same number of atoms (H O) 2 Predicted Law of Multiple Proportions - Not yet discovered - Some elements can combine to give two or more compounds (SO & SO ) 2 3 - Compounds always in smallest whole number - Atoms react as complete particles - Chemical formulas indicate whole number of atoms not fractions Formulas Hardly “out of the blue” Don’t know it at first Formulas and structures backed by lots of experiments Use experiments to find formula and structure Molecular shape can speculate once the formula is known and can be definite from more experiments Chemical Reactions When one or more substances react to form one or more substances Depicted with formulas (Words too long, pictures too awkward Chemical Equations Use chem syms to represent reactions and products - Reactants on left - Products on right - Arrow means yields Coefficients are numbers in front of formula indicate how many of each molecule are reacted or formed Conservation of Mass in Reactions Mass neither created nor destroyed just redistributed Same atoms on both side Balancing Equations Subscripts show how many atoms are there and are static Coefficients show how many molecules there and can be adjusted to balance Ions and Ionic Compounds Ions - Transfer one or more electrons b/t atoms - Electrically charged - You can find the charge of the ion by counting how far the column it is in from the end column (For metals you would start with the first column being a positive one charge and for the nonmetals you start with the column beside the noble gases [the halogens] as being a negative one charge). - Ex. Calcium is in the second column it has a plus two charge (written as Ca ). Ionic Compound - Compound made of ions - Metal and nonmetal Formula Unit - Smallest unit of neutral unit of ionic compound - Smallest whole number ratio Cations – positive Anions – negative Electrical conductivity requires charge movement Ionic compounds are only conductive in aqueous solution Molecular compounds don’t conduct electricity ever; made of uncharged particles Ions of Representative Elements Noble gases stable Nonmetals = negatives Metals = positive Cations of Transition Metals Less reactive Charge of ion less clear Cations of Post-Transition Metals Ga, In, Sn, Tl, Pb, Bi, Uut, Uuq, Uub After transition before metalloids Tin and Lead - Both have two possible oxidation states and both form two compounds with same metal Bismuth only has +3 charge Compounds with Polyatomic Ions Binary - Compounds formed from two elements Polyatomic Ions - Ions made of two or more elements - Ion is negative too many electrons - Positive too few electrons - Formula containing polyatomic follows same rules as ionic - Expressed using parentheses Nomenclature IUPAC standardizes names One system so anyone can reconstruct from name Ionic Cations: + - Metal that forms only one positive ion use English name (Na = Sodium) - Metal that forms more than one use stock system (Au = Gold(II)) Anions: - Monatomic (One atom) anions named by adding -ide to stem (NaCl = Sodium Chloride) - Polyatomic anions use name of the poly atomic ion (NaOH = Sodium Hydroxide) Hydrates Name the ionic compound and give the number of water molecules using a Greek prefix (CaSO 4 * 2H 2 = Calcium Sulfate dihydrate) Molecule Electrically neutral particle Consists of two or more atoms Held by chemical bonds Chemical bonds are attractions that hold atoms together in molecules Shared electrons b/t two atoms Group of atoms that make up molecule behave as singular particle Name describes composition of molecule and specifies number of each atom Molecules vs Ionic Compounds Molecules - Discrete unit (Two Hydrogen to one Oxygen) Ionic - Ions packed as close together as possible --- NaCl has six anions around one cation) --- No ion belongs to another Molecular Compounds Formed of nonmetals A few nonmetals can form millions of different compounds Organic Chem and biochem deal with this in the form of carbon + hydrogen, nitrogen, and oxygen A few only have two atoms (HCl, CO) Most molecules more complex (C H O12 22c11se) Hydrogen Containing Compounds Mlc containing nonmetal and hydrogen # of hydrogen = # of spaces the nonmetal is from a noble gas Organic Compounds Carbon containing compounds Originally thought to only come from living things Hydrocarbons Simplest organic compounds Contain only C & H Alkanes Boiling point increases as Carbon atoms increase Alkenes Hydrocarbons with two less H than alkanes C Hn 2n -ene ending Alkynes Hydrocarbon with 4 less H than alkanes C Hn 2n-2 -yne ending Other Organic Compounds Hydrocarbons are basic building block of organic chemistry Many other classes derived from them Alcohols Replace H in alkane with -OH group In naming, replace -e in alkane name with -ol (ethylane (C H ) to ethanol (C H OH); methane 2 6 2 5 (CH 4 to methanol (CH OH)3 Formulas for Organic Compounds Molecular - Subscript indicates number of each type of atom in molecule (C H (ethan2)6 2 Carbon 6 Hydrogen) - Order of atoms goes; Carbon, Hydrogen, then put elements in alphabetical order) --- EXCEPT ALCOHOLS! --- Emphasize the alcohol by putting the OH group last ALWAYS (C H OH (etha2ol5) Structural - Indicate how carbon atoms are connected (CH CH (etha3e))3 Naming of Molecular Compounds The goal of this naming is a name that translates into a molecular formula (CO ) 2 - Binary --- Which two elements are present? (Carbon and Oxygen) --- How many are present? (1 Carbon and 2 Oxygen) - Format --- First element uses English name; use Greek numerical prefix to indicate how many atoms are there unless there is only one --- Second element uses stem and -ide ending; also has a Greek numerical prefix to indicate how many atoms are present (Mono is omitted unless there is more than one combination; CO and CO ) 2 --- CO – Carbon monoxide --- CO 2 Carbon dioxide Exceptions to This Rule Nonmetal + Hydrogen - No prefixes - Number of hydrogen is found from the periodic table (Find the nonmetal and count the space until the noble gases) - H2Se = Hydrogen Selenide Molecules That Have Common Names - Some molecules have predated names that are still used (H O is wat2r not hydrogen oxide)
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